Cipher block chaining mode
Cipher block chaining is a block-cipher mode that XORs each plaintext block with the preceding ciphertext block before encryption, using an initialization vector for the first block.
Hacking Cryptography
Cipher-block chaining mode XORs each plaintext block with the preceding ciphertext block before encryption, using an initialization vector for the first block.
- How it is used
- Uses CBC to conceal repeated block patterns while motivating implementation failures and attacks.
- How deep it goes
- Derives CBC encryption and decryption, then traces padding-oracle byte recovery and IV-reuse consequences.
- Examples
- Demonstrates penguin-image encryption, an AES-encrypted timestamp service, padding-oracle recovery, and browser requests carrying HTTP cookies.
- What you can do after
- Diagnose/debug with it by identifying IV reuse and padding-validity error leakage in CBC-based services.
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Software Security for Developers
AES-CBC mode is a block-cipher operating mode that chains plaintext blocks through AES encryption using an initialization vector.
- How it is used
- Explains how AES handles multiple blocks while preventing repeated plaintext patterns from appearing in ciphertext.
- How deep it goes
- Details block chaining, key and IV requirements, cleartext IV storage, and the absence of integrity protection.
- Examples
- Uses repeated message sections, two files encrypted under one key, and an IV-ciphertext decryption layout.
- What you can do after
- Evaluate AES configurations, generate unique IVs, and recognize when authenticated encryption is required.
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Real-World Cryptography
Cipher block chaining is a block-cipher mode that XORs each plaintext block with the preceding ciphertext block before encryption, using an initialization vector for the first block.
- How it is used
- Hides repeating plaintext patterns when encrypting multiple blocks with a deterministic block cipher.
- How deep it goes
- Explains IV generation, XOR chaining, padding, encryption, and decryption, but stops short of implementation details.
- Examples
- Uses the ECB penguin, AES diagrams, and an eight-byte padding example.
- What you can do after
- Evaluate/understand how CBC randomizes block encryption and why decryption requires the associated IV.
Read how Real-World Cryptography explains cipher block chaining mode →
Related concepts
- mode of operationkind of · A block cipher mode of operation is a method for applying a block cipher to messages consisting of one or more blocks.
- Galois/Counter Modealternative to · Galois/Counter Mode is an authenticated-encryption mode that combines counter-mode encryption with authentication of ciphertext and associated data.
- data integritycontrasts with · Data integrity is the property that data remains accurate, complete, consistent, and valid, with changes made only through authorized actions.
- initialization vectoruses · An initialization vector is a typically nonsecret value supplied to a cryptographic operation to initialize or vary its processing across uses.
- BEASTused by · BEAST is a browser-based attack against CBC-mode encrypted connections that exploits predictable initialization vectors to recover secret request data.
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